title: Insertion angle impact on primary stability of orthodontic mini-implants.
abstract: OBJECTIVE
  To analyze the impact of the insertion angle on the primary stability of mini-implants.
  
  
  METHODS
  A total of 28 ilium bone segments of pigs were embedded in resin. Two different mini-implant sizes (Dual-Top Screw 1.6 x 8 mm and 2.0 x 10 mm) were inserted at seven different angles (30 degrees , 40 degrees , 50 degrees , 60 degrees , 70 degrees , 80 degrees , and 90 degrees ). The insertion torque was recorded to assess primary stability. In each bone, five Dual-Top Screws were used to compensate for differences in local bone quality.
  
  
  RESULTS
  The angle of mini-implant insertion had a significant impact on primary stability. The highest insertion torque values were measured at angles between 60 degrees and 70 degrees (63.8 degrees for Dual-Top 1.6 mm and 66.7 degrees for Dual-Top 2.0 mm). Very oblique insertion angles (30 degrees ) resulted in reduced primary stability.
  
  
  CONCLUSIONS
  To achieve the best primary stability, an insertion angle ranging from 60 degrees to 70 degrees is advisable. If the available space between two adjacent roots is small, a more oblique direction of insertion seems to be favorable to minimize the risk of root contact.
authors.affiliation: Department of Orthodontics, University of Duesseldorf, Duesseldorf, Germany. wilmes@med.uni-duesseldorf.de
authors.forename: Benedict
authors.initials: B
authors.lastname: Wilmes
authors.forename: Yu-Yu
authors.initials: YY
authors.lastname: Su
authors.forename: Dieter
authors.initials: D
authors.lastname: Drescher
mesh_terms: D000818:Animals; D001863:Bone Screws; D001842:Bone and Bones / Q000601:surgery*; D004868:Equipment Failure; D007085:Ilium; D052280:Orthodontic Anchorage Procedures / Q000295:instrumentation* / Q000379:methods; D016382:Orthodontic Appliance Design; D013552:Swine; D019415:Torque